黄土地基中大直径超长群桩基础受力特性的模型实验研究

Model Experimental Research on Machanical Characteristics of Large Diameter Overlength Pile-group Foundation in Loess

通过室内模型试验,对黄土地基中大直径超长群桩基础的承载-沉降关系、承台下土体附加应力的分布及发展、桩土承载情况以及不同位置桩的受力特性分别进行了研究。结果表明:黄土地基中大直径超长群桩基础荷载-沉降曲线呈缓变型且没有明显拐点,故群桩基础的极限承载力应综合沉降-时间对数s-lgt曲线和荷载-沉降Q-s曲线来确定。承台下土体附加应力分布为边缘大中心小。不同位置的桩承载性能不同,总体上是角桩(6#桩)最大,边桩(5#桩)次之,中心桩(1#桩)最小;同时各桩的桩侧摩阻力及桩身轴力沿桩长的变化也有所不同。

By means of indoor model experiment,the bearing-settlement relation of the large diameter overlength pile group foundation in loess,the soil additional stress distribution and development under pile cap,the pile and soil＇s bearing,the mechanical characteristics of pile at different positions were studied respectively. Results show that the load-settlement curve of large diameter overlength pile group foundation in loess presents a mild change type and has no obvious inflexion. Therefore the ultimate bearing capacity of pile group foundation should be determined by settlement-time logarithm s-lgt curve and load-settlement Q-s curve integratedly. The distribution of soil additional stress under pile cap is big on the edge and small at the center. The bearing behavior of pile at different positions is various：as a whole,the corner pile （6^#pile） is the biggest,the side pile （5^# pile） takes second place,the center pile （1^# pile） is the minimum. Meanwhile,the side friction resistance and axial stress of each pile change diversely along the pile length.